This invention relates to a device made of fibers hollow in the lengthwise direction, for removing waste or noxious material in the blood at high efficiency, and a process of manufacture thereof.
For patients with chronic renal failure, there have been used filter membranes, made of the hollow fibers, in hemo dialyzers; membranes or oxygen suppliers in artificial lungs for exchanging oxygen and carbonic acid gas have been also known.
The prior art, for example as shown in FIG. 1, shows a filter which has a housing 1 containing a plurality of the hollow fiber membranes. The housing has 2 fine holes in walls 3, in which both ends of each membrane are fixed with a potting material made of polyurethane, silicone resin or the like. A blood inlet 4 is provided at one side and a blood outlet 5 at the other side of the housing.
Hemo dialysis is carried out by penetrating the blood of the patient into the hollow fiber membranes 2 through the inlet 4, while the dialyzate is introduced into the housing 1 via an inlet 6, so that undesirable substances in the blood are moved via the membrane wall of the hollow fiber membrane 2 to the side of the dialyzate due to penetration pressure or negative pressure, and removed to the outside through an outlet 7.
The hollow fiber device for removing undesirable substances is in general made according to the following process.
The hollow fibers are stored on polygonal spools to which they are applied from bobbins, and the stored fibers are cut at proper length to make a plurality of bundles. The bundles of the hollow fibers are set in the housing 1, and applied onto their both end portions with a sealing agent, such as polyurethane, and effected with a centrifuge operation (primary centrifugation) so that the end portions are stopped. Subsequently, the potting material such as polyurethane or silicone resin is applied to both ends of the housing 1, and the bundles of fibers are again effected with a centrifuge operation (secondary centrifugation) so that the potting material forming walls 3 is solidified. Then the ends of the hollow fiber bundles are cut transversely according to a required length and made open for blood inlet 4 and outlet 5.
However, in view of the above process, since the fibers are hollow by themselves then when they are cut, the liquid contained therein runs out. Under this condition, if the secondary centrifugation were carried out, the hollow fiber would be made thinner at end portions as shown in FIG. 2 due to the pressure on the potting material of walls 3, accompanying the centrifugal force, or the opening would be deformed as shown in FIG. 2(b), so that it would be difficult for the blood to flow into the hollow fiber 2, and above all blood hemolysis or blood clot could be caused around openings of the hollow fibers, and bubble removal could not be smoothly performed at pliming. Further, since it is not easy for the blood to enter the hollow fiber, the dialytic effect is lowered in a unit dialytic area. Therefore, it is necessary to supply the hollow fibers for heightening the dialytic effect. However, if so, the inlet and outlet must be increased in cross sectional area, resulting in using more of potting agent or making the whole body of the housing heavy in weight. In addition, since the opening of the hollow fiber 2 is deformed in shape as mentioned, the potting material does not perfectly adhere to the outside of the end portions of the fiber so that fine gaps or slits are made and so delamination would easily happen to cause the blood clot or blood stay and lead to a blood leak.
In the prior art, as the membrane wall of the hollow fiber becomes thicker, the above mentioned defects would be remarkable, and prompt resolution has been demanded.